The current application aims to map the medial amygdala (MeA) estrogen receptor alpha (ER?) neurocircuits that are essential for physical activity and body weight control. Our studies will not only advance our current understanding about the physical activity control and the development of obesity in general but also identify new feasible intervention targets for the development of novel therapeutic approaches to combat sedentary behaviors. Therefore, this proposed research is directly relevant to public health and the NIH's mission. I have four years of postdoctoral research experience when submitting this application (07/2011-07/2015). My long- term goal is to establish myself as an independent investigator in the area of central regulation of physical activity and metabolism. In order to develop an independent researcher in this field, I will use my K99-funded mentored period to (1) gain new training in exercise physiology to compare different aspects of treadmill exercise and voluntary wheel running behavior in mouse model; (2) implement the most advanced knowledge about physical activity/metabolism and cutting-edge techniques in the field of central regulation of metabolic behavior; (3) advance grantsmanship, project and laboratory management skills, mentoring, teaching skills, etc. I will start looking for university faculty positions towards the end of the first year of the K99 stage to ensure the smooth transition to the R00 phase. The ovary hormone, estrogen, plays an important role in maintaining normal energy homeostasis by regulating food intake and physical activity. While ER? expressed by pro-opiomelanocortin (POMC) in the hypothalamic arcuate nucleus (ARC) modulates food intake, estrogen- responsive neurons influencing locomotion remain undefined. Recently, we demonstrated that ER? expressed by the Single Minded 1 (SIM1) neurons in the MeA dedicated to promoting locomotion in both males and females. Additionally, acute activation of MeA SIM1 neurons led to short term increase of locomotion. These suggest that ER? expressed by MeA SIM1 neurons constitute part of a previously undefined locomotor circuit that is used in both males and females. Here, we plan to further define and understand how this MeA estrogen- responsive neural circuit promotes locomotion. In the aim 1 and 2 (K99 phase), we will (1) test if ER? in the MeA is required for the coordinated control of locomotor activity, body weight and exercise-induced metabolic benefits by using mouse/virus genetic loss-of-function and gain-of-function models to specifically delete or overexpress whole ER? population in the MeA; (2) further demonstrate if activation/inhibition of MeA ER? neurons increases/decreases locomotion by using a novel technology termed Designer Receptors Exclusively Activated by Designer Drugs (DREADD). With this information in hand, we will then start aim 3 (R00 phase) to map the downstream neural circuits of MeA ER? neurons and identify the critical MeA downstream neural circuits where estrogen acts to stimulate locomotion and prevent obesity. The proposed studies represent logical extensions to our previous work and offer an excellent opportunity to understand the neural basis of estrogenic regulation of locomotion, not only in females but also in males.